Most modern engines are direct injection engines, which means that each combustion cylinder of the engine includes a dedicated fuel injector configured to inject fuel directly into a combustion chamber. While direct injection engines represent an improvement in engine technology over past designs, in the form of increased engine efficiency and reduced emissions, the improvement of the design of any particular engine is always desirable, especially in light of increasing fuel costs and ever more strict regulations on engine emissions.
In a traditional direct injection engine, one or more fuel jets that are injected into a combustion chamber interact with various combustion chamber structures, which cause the fuel to disperse into the combustion chamber. More specifically, the fuel jet(s) entering the combustion chamber impact various surfaces of the combustion chamber such as a piston bowl, the flame deck surface of the cylinder head, the cylinder liner or bore, and other surfaces before spreading in all directions. The impingement of the fuel jets with these structures may have a variety of effects including increased emissions because localized areas having higher fuel concentrations may burn rich while other areas on the cylinder may burn lean. This can further result in higher temperatures, decreased fuel efficiency, increased heat rejection and component temperatures, and the like.
Various solutions have been proposed in the past for improving an engine's efficiency and reducing its emissions. One example of a previously proposed solution can be seen in U.S. Pat. No. 9,091,199 (“Straub”), which was granted on Jul. 28, 2015. Straub describes a combustion chamber that includes a piston forming deflection foils. The deflection foils, according to Straub, operate to distribute a fuel spray into portions directed toward one of the deflection foils, which redirect their respective portion of the fuel spray into a combined radial path that swirls about a center of the combustion. In the described embodiment, Straub explains that the fuel spray is thus directed substantially tangential relative to the combined radial path of the redirected portions of the fuel spray. While the flow redirection of Straub may be partially effective in improving mixing of air with incoming fuel in the combustion chamber, the momentum of the redirected fuel spray is maintained generally parallel to a top piston surface such that the induced swirling may cause fuel to migrate towards a cylinder wall. Maintaining the fuel close to the piston may also increase heat rejection while the fuel is burning.